1. Field of the Invention
This invention relates to the identification of cells by electrophoresis. More particularly, the invention relates to a system for cell identification which can be easily used by semi-skilled workers and yet produce consistently reproducible results.
2. Description of the Prior Art
The identification of biological cells has been a long standing problem in the biological sciences. A variety of techniques have been applied to the problem. For example, infectious microorganisms have been identified in clinical laboratories by means of simultaneously applied biochemical reactions. Vertebrate, plant and mycoplasma cells have been characterized in some research laboratories by specilized techniques including sophisticated isoenzyme electrophoresis, cell surface antigen analysis and chromosome analysis.
The problem of identifying cells is particularly acute when cells are grown in tissue culture. Because the tissue culture medium is designed to encourage cell growth, it is highly susceptible to contamination. As a result, a tissue culture thought to be growing a particular type of cell, in fact, through contamination, can be growing either a combination of the original cells and the contaminating cells, or, depending on the relative viability of the original cells and the contaminating cells, just the contaminating cells. Accordingly, when a researcher conducts experiments and reaches conclusions based on tissue culture work, and couples those results and conclusions to a particular type of cell, he may be misleading both himself and the public with regard to his work. Numerous examples of such contamination have been documented in the biological literature. Indeed, in 1976, it was reported in the American Journal of Hematology that approximately 30% of a series of tissue culture cells studied were incorrectly designated by the submitting investigator. See C. S. Stulberg, W. D. Peterson, Jr., and W. F. Simpson, "Identification of Cells in Culture", American Journal of Hematology, Volume 1, pages 237-242 (1976).
The problem of contamination of tissue culture cells was identified at least as early as the late 1960's. See, for example, S. Gartler "Apparent HeLa Cell Contamination of Human Heteroploid Lines," Nature, Volume 217, pages 750-751 (1968). Yet, reports of contaminated tissue culture cells continue to appear in the literature. See, for example, D. Dickson, "Contaminated Cell Lines", Nature, Volume 289, page 227 (1981).
Of significance with regard to each of these reports of contaminated tissue culture cells is the fact that the contamination was found only by means of highly sophisticated and time consuming procedures using expensive equipment in the hands of experts in the area of cell identification. Moreover, none of the procedures used by these experts included provisions for standardization of the system or provisions for the inclusion of a control to verify the performance of the system. Also, in order to confirm any cell identification, these investigators maintained large stocks of reference cells. For all of these reasons, the procedures previously used for identification of cells have not been reproducible enough in various investigators' hands to be of general utility.